Known transport networks use circuit oriented technologies (eg Synchronous Digital Hierarchy (SDH) and more recently wavelength switching) and include sophisticated restoration schemes, including double path protections (eg Sub-Network Connection Protection (SNCP)), bandwidth sharing restorations (eg supported by control planes Automatically Switched Transport Network (ASTN)/Generalised Multi-Protocol Label Switching (GMPLS)) and even dual ended restorations (eg International patent application WO 2005/081435 A1).
A major application of transport networks is to provide support to a packet network interconnection (eg backbone Internet Protocol (IP) routers). In this application, it is known to engineer the IP network already with its own resilience schemes. These generally account for the totality of reliability of IP backbone networks, and in transport networks unprotected connections are used.